quick sensing and subsequent controlling of the amount of oxygen (O.sub.2) in a combustion product gas is necessary in various situations. For example, most engine test facilities in the U.S. use vitiated (oxygen enriched) combustion products expanded to either subsonic, supersonic, or hypersonic speeds to test and validate engine operation. To conduct nominal Mach 7 flow wind tunnel testing of air-breathing propulsion systems, the oxygen content of the combustion product flow gas must be equivalent to the oxygen content of the air. Too much oxygen may damage the engine; too little oxygen will result in reduced impulse. Also, this sensing of the amount of O.sub.2 in the combustion product gas must be accomplished in a time interval smaller than the flow delivery system response and in a time frame that is a small fraction of the run time. Run times are often approximately 20 seconds.
Current O.sub.2 sensing devices do not have response times which are quick enough to be utilized during such small time periods They are usually designed for use in boiler operations or steady state industrial processes where time is not of the essence. Currently available sensors have a response time of approximately five seconds. A sensor system response time of at least a quarter of a second is required in the above application. Such a sensor response time approximates real time since the response time of the valve controlling the amount of O.sub.2 in the combustion chamber is about 0.25 second.
Accordingly, it is an object of this invention to quickly sense the amount of oxygen in a combustion product gas.
It is a further object of this invention to achieve the object in order to control the amount of oxygen in the combustion product to maximize efficiency and minimize pollution.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings which follow.